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Research Profile: Kamal Khabbaz, MD

Kamal R. Khabbaz, MD

David S. Ginsburg Associate Professor of Surgery in the Field of Cardiothoracic Surgery

Chief of Cardiac Surgery

Research Group

Louis Chu MD
David Liu MD
Feroze-ud-Den Mahmood MD

Research Focus

The Valve Research Group primarily investigates the dynamic behavior of heart valves in both normal and pathologic states. Heart valves are complex 3-dimensional (3D) structures that undergo dynamic changes during the cardiac cycle. Investigating this behavior is of critical importance in understanding the pathophysiology of and devising management strategies for valvular disease.

Together with Dr. Feroze Mahmood and a multidisciplinary Valve Research Group, normal and abnormal size, shape, and geometric parameters pertaining to the mitral, tricuspid, and aortic valves are being researched. In addition, we are studying the impact different surgical interventions (e.g., aortic valve replacement and mitral annuloplasty) have on native valve function and surrounding anatomy. To accomplish this, we analyze 3D echocardiographic data using commercially available software, including Philips Qlab and TomTec Image Arena. These software programs enable us to dynamically track and measure anatomical changes in a clinically feasible fashion.

We are currently in the process of extending similar analyses to normal and pathologic tricuspid valves, leading to a more robust understanding of tricuspid valve behavior. Investigations are also underway to investigate the in vivo effects of different annuloplasty devices on dynamic valve motion and geometry. These data and analyses hold significant potential in furthering the evidence base for valve repair strategies and surgical decision- making toward achieving the best outcomes.

The multidisciplinary Valve Research Group is involved with multiple national and international universities, engaged in devising new methods of interrogating valvular structures using 3D echocardiography. We are continuing our collaboration with Cardiology and Vascular and Endovascular Surgery on multiple projects including clinical trials, which include the following:

Multi-Center Experience with the Rapid Deployment EDWARDS INTUITY Valve System For Aortic Valve ReplaceMent (TRANSFORM Trial, Protocol Number 2011-02): The purpose of this clinical investigation is to assess the safety and effectiveness of the investigational EDWARDS INTUITY Valve System in subjects with aortic stenosis or stenosis- insufficiency requiring replacement of the native aortic valve.

Clinical trial of the on-X valve using low dose anticoagulation: The purpose of this study is to define the lowest level of required antithrombotic therapy for mitral or aortic valve replacement using the On-X Valve.

Medtronic Core Valve U.S. Pivotal Trial – Extreme Risk Patients; Medtronic CoreValve® U.S. Pivotal Trial – High Risk Surgical Patients; Medtronic CoreValve® U.S. Continued Access Study; Medtronic CoreValve® U.S. Expanded Use Study; Medtronic CoreValve® SURTAVI Trial: The purpose of this study is to determine the safety and efficacy of the Medtronic CoreValve® System in the treatment of symptomatic severe aortic stenosis in high-risk and very high-risk subjects who need aortic valve replacement.

Early Feasibility Study of the CardiAQ™ Transcatheter Mitral Valve (TMV) System with Transseptal Delivery System for the Treatment of Moderate to Severe Mitral Regurgitation

Evaluation of Xience versus Coronary Artery Bypass Surgery for Effectiveness of Left Main Revascularization

Accomplishments 2016-2017

Several studies are in progress. Studies completed so far have shown promising results. The results of one study demonstrate that left-ventricular outflow tract area is signiﬁcantly underestimated by two-dimensional (2D) measurements when compared with 3D data. This underestimation of the LVOT area with 2D echocardiography potentially overestimates the degree of aortic stenosis (AS). Such errors in assessing disease severity can have important clinical consequences vis-à-vis the decision to operate vs. not operate.

In another study, we report that the implantation of prosthetic valves in the aortic position is associated with changes in dynamic mitral annular geometry. Earlier, our understanding of the effects of aortic valve replacement was limited to geometric analyses of mitral annular conformation at a single point in the cardiac cycle (end-systole).

We have also successfully demonstrated the use of 3D echocardiography in analyzing mitral valve geometry in patients with functional mitral valve regurgitation (FMR). Previously, the understanding of annular dynamics in FMR was largely limited to information derived from animal models.

The Valve Research Group has been recognized and granted the status of hospital “core laboratory” for 3D printing establishing a state-of-the-art 3D printing laboratory. Additionally multiple echocardiography simulators serve as a dedicated simulation laboratory.

Teaching, Training, and Education

As Program Director of the BIDMC Cardiothoracic Surgery Residency Program, I have trained 21 cardiothoracic surgical fellows. Three have gone on to become Chairman or Chief of Cardiothoracic Surgery at their respective institutions; one has become Director of Minimally Invasive Surgery. This training includes weekly seminars, direct operative supervision, teaching cardiac surgery techniques, innovations in percutaneous valve mitral valve repair, and new aortic valve deployment techniques.

I also teach BIDMC General Surgery residents (PGY-2, PGY-3) in cardiac surgery techniques, and continue to teach a course on echocardiography at Harvard Medical School. In addition, I teach third- and fourth-year HMS students rotating on cardiothoracic surgery and an elective in thoracic and cardiovascular surgery for fourth-year HMS students.